接地网圆钢杆中高频纵向超声导波无损检测方法研究

On the Nondestructive Examination of Round Steel Bar in Grounding Grid using High-Frequency Longitudinal Ultrasonic Guided Wave

针对接地网圆钢杆腐蚀检测问题,本文进行了接地网圆钢杆高频纵向超声导波无损检测方法研究。首先对埋地环境下圆钢杆中纵向导波传播特性进行理论研究,分析了不同模态导波的群速度和衰减频散特性。研究发现,高阶纵向模态导波在衰减最小和群速度最大对应的频率处,在圆钢杆中传播能力强,是适合进行地埋圆钢杆导波检测试验的频率范围。在此基础上,进行了埋地圆钢杆高频纵向超声导波无损检测试验研究。结果发现,利用优选的检测参数可以很好地实现埋地圆钢杆中腐蚀缺陷检测。研究工作为接地网运行状态评价提供了很好的技术支撑。

A nondestructive examination method using high-frequency longitudinal ultrasonic guided wave was developed to detect the corrosion defects in round steel bar used in grounding grid. Firstly, theoretical analysis of the propagation characteristics of longitudinal guided wave in round steel bar buried in soil was conducted, which focused on the guided wave group velocity in different modes and its frequency dispersion and attenuation characteristics. It is found that guided wave in higher order longitudinal mode corresponds to a frequency, where its attenuation reaches the minimum value and its group velocity reaches the maximum value, and presents better propagation capability at this frequency. So, this frequency range is suited for nondestructive examination for round steel bar. Based on above results, nondestructive examination for round steel bar buried in soil using high- frequency longitudinal ultrasonic guided waves was conducted. Results show that, using the preferred detection parameters, the corrosion defect detection in round steel bar buried in soil can be well achieved. Above study may provide a possible technical support for grounding grid working condition evaluation.